1. Field of the Invention
The present invention generally relates to an oil recovery device and method of use. More specifically, the present invention relates to an oil recovery device and method of use whereby a submersible pump is driven by a hydraulic motor.
2. Background Information
The use of oil recovery devices are known in the art. More specifically, oil recovery devices heretofore devised and utilized are known to consist basically of familiar, expected and obvious structural configurations, notwithstanding the myriad of designs encompassed by the crowded prior art which have been developed for the fulfillment of countless objectives and requirements. While these devices may fulfill their respective, particularly claimed objectives and requirements, the aforementioned documents do not disclose an oil recovery system and method of use such as Applicant's present invention.
There is a wide variety of devices used for the recovery of oil. A reason for this is that each different type of pump may be especially beneficial (for one reason or another) for a particular application in the oil recovery process.
A particular type of oil recovery pump is known as a progressive cavity, or “PC,” pump. PC pumps are generally characterized by a central, elongated shaft member having a continuous, spiral-type flange spanning the length of the central shaft member. As the central shaft rotates, the associated spiral-type flange rotates and carries recovered oil along the central shaft from bottom to top. The configuration of PC pumps lends itself to the recovery of multi-viscosity oils and is particularly applicable for recovering heavy (low gravity) oil. As will be further discussed, the recovery of “heavy oil” is associated with several types of problems and inefficiencies, the large majority of which are solved or overcome in elegant fashion by Applicant's invention.
Today, submersible oil pumps (those such as PC pumps), are driven by an alternating current “AC” electric motor. This is typically the case as the cumulative resistance along the length of electric cable extending between the surface power source and the downhole pump renders the use of direct current “DC” motors impractical. The use of AC motors presents limitation not yet overcome by known devices. Without the use of variable frequency drives (which use has proven to be impractical), the operating range of these motors is very limited (typically between 55 Hz and 65 Hz for motors known to be used in the art). This limited range necessitates that the motor operate with near constant speed. As will be further described, this type of operation leads to several problems, all of which are overcome by the present device.
Problems associated with recovering heavy oil are often exaggerated during initial stages of operation. For instance, AC motors cannot “ramp up,” but instead immediately proceed to running speed. This causes undue acceleration of the surrounding production oil into and through the pump. All too often, the accelerated oil carries solids into the pump where they can become trapped within pump components. The results can be devastating; as trapped solids often cause a complete lock down of the system whereby the device must be removed from the well, repaired at the surface, and then relocated before operation may recommence. In addition, seemingly unavoidable limitations arise as the pump produces and approaches it's intended production and fluid level design parameters. As the oil level descends, the pressure differential between downhole and surface increases, requiring more horsepower to produce the same amount of produced fluid. Because AC motors run at constant speed, they are unable to compensate for falling oil levels to efficiently produce and maintain a desired fluid level and production rate.
Applicant's invention, through a novel combination of component pieces, provides an efficiency in the recovery of oil not available with known devices. For instance, during initial startup, a high fluid level causes the pump to produce at a greater efficiency due to increased pump suction pressure. This allows the produced fluid to surge into the well bore, in some cases bringing unwanted solids. To prevent production surges, the hydraulic motor should be initially operated at relatively low speed. From there, motor speed may gradually “ramp up” to full operation speed. This is thought to be particularly beneficial when used in oil wells containing relatively dense production fluid, or oil having a large amount of solids (such as sand). The gradual increase in motor speed during initial operation provides for a gradual uptake of production oil through the pump. This gradual uptake largely eliminates the influx of solids into the device, thereby providing for increased operating efficiency and longer operating life. In the event that solids are ingested within the device and causes operational problems, the operational direction may easily be reversed. This feature, not available with any known devices, has a tremendously beneficial impact. Rather than having to remove, repair, and reposition the recovery device, the pump direction may be reversed so that any trapped solid becomes dislodged as it is “backed out.”
The present invention provides other novel benefits as well. Optimally, as the producing annulus fluid decreases as the pump runs, increased horsepower should be gradually applied to maintain a constant rate and pumping fluid level. With known devices (which operate at constant speed), a compromise has to be made to prevent well from “pumping off” or pumping with a high fluid level. The operational speed of the device may easily be increased in corresponding fashion to maintain a constant production volume or fluid level by increasing the hydraulic power flow at the surface.
The novelty of the present invention is perhaps best understood by way of example. Currently, a university research team is collaborating to solve the very problems mentioned above. This team has invested a tremendous amount of man power and money to solve these problems, yet have been unable to do so. Applicant's invention, through a novel combination of component pieces, provides an elegant solution to the problems mentioned above.
Further, it is well known to those skilled in the art that there is a tremendous amount of underground heavy oil that cannot be produced with economic efficiency in view of the problems mentioned above. Currently, Canada is believed to have the largest known reserve of heavy oil in the world; however, production is not feasible with known technology. Applicant's invention, however, is believed to overcome known problems with such efficiency that production should commence in wells with even the “heaviest oil.”
In view of the problems associated with known recovery devices and methods, a great need exists for an oil recovery device that can withstand the rigors of recovering oil containing a relatively large amount of solid matter. Applicant's invention provides such a device and method. That is, the present invention is capable of variable speed and reversible operation. As such, oil can be gradually accelerated through a submersible pump and solids that become trapped in pump components can be “backed out” and allowed to redistribute away from the pump.